Abstract: In a conditional discrimination (matching-to-sample), a sample is followed by two comparison stimuli, one of which is correct, depending on the sample. Evidence from previous research suggests that if the stimulus display is maintained following an incorrect response (the so-called penalty-time procedure), acquisition by pigeons is facilitated. The present research tested the hypothesis that the penalty-time procedure allows the pigeons to review and learn from the maintained stimulus display following an incorrect choice. It did so by including a penalty-time group for which, following an incorrect choice, the sample changed to match the incorrect comparison, thus providing the pigeons with post-choice 'misinformation.' This misinformation group acquired the matching task significantly slower than the standard penalty-time group (that had no change in the sample following an error). Furthermore, acquisition of matching by a control group that received no penalty time fell midway between the other two groups, suggesting that the pigeons did not merely take more care in making choices because of the aversiveness of penalty-time. Thus, it appears that in the acquisition of matching-to-sample, when the stimulus display is maintained following an incorrect choice, the pigeons can review or acquire information from the display. This is the first time that such an effect has been reported for a nonhuman species.

Abstract: Divergent choose-absence retention functions typically found in pigeons following presence/absence-sample matching have been attributed to the development of a single-code/default coding strategy. However, such effects may result from adventitious differential responding to the samples. In Experiment 1, retention functions were divergent only when differential sample responding could serve as the basis for comparison choice. In Experiment 2, when pecking did not occur during the retention interval, a choose-absence bias was found, but when pecking occurred during the retention interval, a choose-presence bias resulted. In Experiment 3, positive transfer was found when a stimulus associated with the absence of pecking replaced the absence sample but not when a stimulus associated with pecking replaced the presence sample. Thus, presence/absence-sample matching may not encourage the development of a single-code/default coding strategy in pigeons.

Abstract: The traditional notion of aggression as an antisocial instinct is being replaced by a framework that considers it a tool of competition and negotiation. When survival depends on mutual assistance, the expression of aggression is constrained by the need to maintain beneficial relationships. Moreover, evolution has produced ways of countering its disruptive consequences. For example, chimpanzees kiss and embrace after fights, and other nonhuman primates engage in similar “reconciliations.” Theoretical developments in this field carry implications for human aggression research. From families to high schools, aggressive conflict is subject to the same constraints known of cooperative animal societies. It is only when social relationships are valued that one can expect the full complement of natural checks and balances.

Abstract: According to the “public information” hypothesis, some animal species may monitor the current reproductive success of conspecifics to assess local habitat quality and to choose their own subsequent breeding site. To test this hypothesis experimentally, we manipulated two components of public information, the mean number of offspring raised locally (“quantity”) and their condition (“quality”), in the collared flycatcher Ficedula albicollis. Immigration rate decreased with local offspring quantity but did not depend on local offspring quality, suggesting that immigrants are deprived of information regarding local quality. Conversely, emigration rate increased both when local offspring quantity or quality decreased, suggesting that residents can use both components of public information.